In frequency modulation (FM) wireless devices, in order to set the maximum modulation degree (maximum frequency shift) in frequency modulation to be equal to or less than a prescribed value, an instantaneous deviation control (IDC) circuit is provided. A carrier wave is frequency-modulated in accordance with an output of the IDC circuit. This IDC circuit includes a limiter circuit and a splatter filter. In the limiter circuit, the amplitude of the input signal to the IDC circuit is restricted, and harmonic components produced at the limiter circuit are suppressed by the splatter filter.
In the wireless transceiver device disclosed in Unexamined Japanese Patent Application Kokai Publication No. S61-265930, sound signals from a microphone are frequency differentiated by a pre-amplifier and a pre-emphasis circuit, and a high-level signal is clipped by a limiter amplifier. In addition, the splatter filter suppresses harmonic components produced by clipping. The limiter amplifier and the splatter filter constitute the IDC circuit.